1. Field of the Invention
This invention relates to a connector, more particularly to a connector which is suitable for high-speed transmission of electric signals.
2. Description of the Related Art
Conventionally, there has been proposed a receptacle connector comprised of three types of contacts, an insulator for holding the contacts, and a receptacle shell for covering the insulator (see Japanese Laid-Open Patent Publication (Kokai) No. 2002-334748).
The three types of contacts include a signal contact S and a ground contact G for high-speed transmission, and a contact D for non-high-speed transmission. Each of the three types of contacts has contact portions which are capable of being brought into contact with contact portions of mating contacts of a mating connector, and terminal portions which are capable of being soldered to pads on a printed board.
The contact portions are arranged in two rows, one above the other (see FIG. 7(b) in the above-mentioned Patent Publication). In the upper row, the contact portions are disposed in the order of D, D, D, G, S, S, G, S, and S from the left side as viewed from the front side of the insulator. In the lower row, the contact portions are disposed in the order of D, D, S, S, G, S, S, and G from the left side as viewed from the front side of the insulator. One ground contact G in the upper row and a pair of signal contacts S and S in the lower row which are located below the ground contact G form one contact group for high-speed transmission, while one ground contact G in the lower row and a pair of signal contacts S and S in the upper row which are located above the ground contact G form one contact group for high-speed transmission.
The terminal portions are arranged in a row along the direction of the width of the insulator (the contact arranging direction) (see FIG. 7(a) in the above-mentioned Patent Publication). In this row, the terminal portions are disposed in the order of D, D, D, D, D, S, G, S, S, G, S, S, G, and S from the left side of the insulator. One ground contact G and a pair of signal contacts S and S located on opposite sides of the ground contact G form one contact group for high-speed transmission.
In the above-described arrangement of the contact portions, only the pair of signal contacts S located at a right end in the upper row are not in a state sandwiched by ground contacts G. As a result, variation in transmission characteristics is caused between the pair of signal contacts S and the other pairs of signal contacts, and there is a fear that crosstalk may occur between the pair of signal contacts S and other pairs of signal contacts located obliquely below.
Further, in the arrangement of the terminal portions, the signal contacts of adjacent contact groups in the direction of the width of the insulator are adjacent to each other, and hence there is a fear that crosstalk occurs between these signal contacts.
Furthermore, since the terminal portions are arranged in a row along the direction of the width of the insulator, the connector suffers from the problem of an increase in size.